How to test for front/back focus?
If anyone can link to an article that tells how to test for front or back focus, that would be helpful. I have several camera/lens combinations I want to test. I want the test itself to be accurate and objective so as not to throw another variable into the mix.
Nikon user since 2000
#1. "RE: How to test for front/back focus?" | In response to Reply # 0alberte Nikonian since 19th Dec 2004Mon 27-Jul-09 06:45 PM
Albert Esschendal - Nikonian in Hengelo(O.), The Netherlands
Nikonians Moderator: D5/D4/D3/D2/D1 Users Group, D300/D200/D100 Users Group, Nikkor Autofocus Lenses and Dutch Cafe Moderator
Website: Albert Esschendal Photography
#2. "RE: How to test for front/back focus?" | In response to Reply # 1ZoneV Nikonian since 07th Jan 2005Mon 27-Jul-09 07:47 PM | edited Mon 27-Jul-09 07:49 PM by ZoneV
For some reason the links wouldn't work for me. I am going to copy and paste. I still cannot view the first one.
Nikon user since 2000
#3. "RE: How to test for front/back focus?" | In response to Reply # 2Len Shepherd Nikonian since 09th Mar 2003Tue 28-Jul-09 05:22 PM
As regards this chart the number 1 at canon USA is far from complimentary
Chuck Westfall “I recommend using a flat, detailed target parallel to the focal plane. After reading through the PDF linked from your message, it appears that the author has missed a major point, i.e., any individual focusing point in a digital SLR is much longer than the simple line he is using on his chart. The nature of the AF sensors used by EOS digital SLR’s as well as those from other manufacturers is that they perform most reliably when the entire length of the focusing area sees readable detail. This condition is not satisfied by a thin line on a piece of paper. It's OK to include an angled chart in a test photo. In fact, Canon Factory Service Centers always do this. But the test target is always separate from the angled chart, and parallel to the camera's focal plane”.
Nikon also imply (in example 2 of their AF guidance on sharp contrasting detail) mis focus by the camera AF (not the same as front or back focus) is possible
In my view there is little point in testing for front or back focus unless you can be sure AF is 100% accurate.
With Nikon AF-s lenses with good AF targets AF accuracy is around 0.03% of focus distance - an accuracy that needs no or negligible fine tune.
With a poor AF target my initial tests indicate AF can be off sufficient to reduce resolution 10-15% - and using fine tune to "correct" then reduces resolution with a good AF target 10-15%.
Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.